close all;clear;clc;
t = 1900:10:2000;
y = [76 92 106 123 132 151 179 203 227 250 281];
p = polyfit(t,y,2);
S = poly2str(p,'t')
Y = polyval(p,t);
alpha = 2.0274e-09;
beta = 0.0128;
y2 = alpha.*exp(beta.*t);
P0 = plot(t,y,'rh');
P0.MarkerSize = 10;
hold on
P1 = plot(t,Y,'b-');
P1.LineWidth = 1;
P2 = plot(t,y2,'k-.');
P2.LineWidth = 1;

grid on
xlabel('时间\rightarrow')
ylabel('人口（百万）')
title('\fontname{隶书}\bf\it\fontsize{12} XX国的人口数据')
legend({'离散点','y=at^2 + bt + c','y = \alpha e^{\beta t}'})
